One popular plot is the discovery of a common enemy that forces Superman and Homelander to team up, despite their differences. Another is a battle for supremacy in a world where both exist, with different factions taking sides. And then there's the plot where Superman tries to reform Homelander, seeing the potential for good in him.
Well, it depends on how the fanfiction is written. If it's a more 'grounded' version where Homelander's public image and mind - games play a big role, he could potentially gain an upper hand. But generally, Superman has more raw power. He can move planets, and his speed is almost limitless. Homelander is strong and has flight and heat vision too, but Superman just seems to be on a whole other level in terms of pure power.
Well, I think Bumblebee would have a shot at winning in a battle of wits. Bumblebee has been shown to be very adaptable. In a fanfic, he could use his knowledge of Megatron's weaknesses, like his overconfidence. Bumblebee might pretend to be more vulnerable than he really is, luring Megatron into a false sense of security. Then, when Megatron least expects it, Bumblebee could strike with a clever plan. Megatron, on the other hand, is used to being in control and might not expect such a devious tactic from Bumblebee.
A really dramatic plot twist could be if Bumblebee and Megatron had to team up in the fanfic. Maybe there's a greater threat that neither of them can face alone. It would be so unexpected because they're enemies. Bumblebee would have to put aside his hatred for Megatron, and Megatron would have to trust Bumblebee at least a little bit.